The reproductive strategy of the slender loris varies slightly from that of the other loris species. While most individuals live alone, some also live in pairs. There are two distinct mating seasons in the wild, one from April to May and another from October to November. In captivity, the slender loris breeds year round. During mating season, the female is in estrus for a period of 29-40 days. During mating the female hangs from a branch by all four limbs and will completely support the male’s weight, in addition to her own.
Gestation ranges from 166-169 days. Mothers normally give birth to one infant at a time, but twins have been reported at a rate of about 22%. Newborns cling to their mothers’ fur and are born pink and almost entirely furless. The maternal instinct is apparently strong, as captive females have been observed caring for the infants of other females.
Offspring reach sexual maturity between 10 and 18 months (more slowly in males) and may give birth themselves soon after.